On a sunny day, Mary (Rachel Melvin) brought two friends, Jane (Lexi Atkins) and Zoe (Cortney Palm), to her cousin's cabin in a forest for vacation. Jane had just broken up, and they hoped that their friends could forget all their worries and sorrows in the leisurely place with clear water and blue sky. The girls played happily and carefree. Before long, Jane's boyfriend Sam (Hutch Dano) and Tommy (Jake Weary), Buck (Peter Gilroy) and other boys also followed. This holiday seemed to be so beautiful, but the terrible disaster came quietly. Previously, the discarded drugs of a medical institution accidentally flowed into the valley stream, causing all the local beavers to become cruel, brutal and bloodthirsty monsters. Death trap, no one can escape...